Add a small example of how Shadow CLJS can break

At this commit, the app compiles, yet at run time the app does not
show the expected elements but instead throws a mysterious exception
that states:

    An error occurred when calling (test-evergreen.core/init)

This problem is triggered by the difference between how Shadow CLJS
resolves dependencies and how Node.js does it.

In a nutshell, Node.js supports multiple versions of a single
package within a single project; Shadow CLJS does not. And in this
short example, that makes all the difference.

In our project, we are experiencing significant pain due to this
limitation. I thought it would be worth sharing with the community a
simplified example to indicate why this constraint is difficult to
manage.

In the case of this particular commit, here are the relevant
dependencies and versions:

- our app depends on evergreen-ui at ^6.0.1 (currently the latest)
- [email protected] depends on:
  - glamor at ^2.20.40 (currently the latest) and
  - ui-box at ^4.0.0 (latest is 4.1.0)
- [email protected] depends on inline-style-prefixer at ^3.0.6
- [email protected] (the latest) depends on inline-style-prefixer at
  ^5.0.4

It turns out that inline-style-prefixer (abbreviated ISP from now
on) moved its modules around at version 5.0.0, so the way that
glamor requires ISP works for pre-v5 but not v5 and later.
Conversely, the way that ui-box requires ISP works for v5 and later
but not pre-v5.

**So there's no single version of ISP that works for both
dependencies.** And neither dependency can be easily jettisoned,
because they're both required by a dependency (evergreen-ui) that is
maintained by others.

What can we do? For starters, I've opened a PR for glamor to use a
post-v5 version of ISP. Hopefully they'll accept my PR and release a
new version soon. In the meantime, I can vendor my fork of glamor
into the repo and depend on the vendored version instead of the
version on NPM. That approach is shown in the next commit.

.gitignore

@@ -0,0 +1,3 @@
+node_modules
+.shadow-cljs
+resources/public/js/compiled